The present invention relates to cache memory management and snapshot operations in a data storage system.
This application also incorporates by reference herein as follows:
U.S. application Ser. No. 10/264,603, Systems and Methods of Multiple Access Paths to Single Ported Storage Devices, filed on Oct. 3, 2002, now abandoned;
U.S. application Ser. No. 10/354,797, Methods and Systems of Host Caching, filed on Jan. 29, 2003, now U.S. Pat. No. 6,965,979 B2;
U.S. application Ser. No. 10/397,610, Methods and Systems for Management of System Metadata, filed on Mar. 26, 2003, now U.S. Pat. No, 7,216,253 B2;
U.S. application Ser. No. 10/600,417, Systems and Methods of Data Migration in Snapshot Operations, filed on Jun. 19, 2003, now U.S. Pat. No. 7,136,974 B2;
U.S. application Ser. No. 10/616,128, Snapshots of File Systems in Data Storage Systems, filed on Jul. 8, 2003, now U.S. Pat. No. 6,959,313 B2;
U.S. application Ser. No. 10/677,560, Systems and Methods of Multiple Access Paths to Single Ported Storage Devices, filed on Oct. 1, 2003, now abandoned;
U.S. application Ser. No. 10/696,327, Data Replication in Data Storage Systems, filed on Oct. 28, 2003, now U.S. Pat. No. 7,143,122 B2;
U.S. application Ser. No. 10/837,322, Guided Configuration of Data Storage Systems, filed on Apr. 30, 2004, now U.S. Pat. No. 7,216,192 B2;
U.S. application Ser. No. 10/975,290, Staggered Writing for Data Storage Systems, filed on Oct. 27, 2004;
U.S. application Ser. No. 10/976,430, Management of I/O Operations in Data Storage Systems, filed on Oct. 29, 2004, now U.S. Pat. No. 7,222,223 B2;
U.S. application Ser. No. 11/122,495, Quality of Service for Data Storage Volumes, filed on May 4, 2005;
U.S. application Ser. No. 11/245,718, A Multiple Quality of Service File System, filed on Oct. 8, 2005; and
U.S. application Ser. No. 11/407,491 Management of File System Snapshots, filed Apr. 19, 2006.
A data storage system may use snapshots for backup, data mining, or testing of software programs in development. A snapshot is a usable image of the data at an instant in time. The snapshot results in two data images: (1) the original data that can be read and written by applications as soon as the snapshot is created, and (2) the snapshot that can be backed up or mined. Some techniques allow a snapshot to be modified while others create read-only images. One technique of snapshot is copy-on-write. In copy-on-write, upon getting a request to store modified data, the data storage system first copies the original data to a target storage space before permitting the modification to be written to its source storage space. The need for high data availability in data storage systems may require making frequent snapshots of data. However, frequent snapshots consume system resources such as cache memory, the internal memory bandwidth, storage device capacity and the storage device bandwidth.